Field of the Invention
Embodiments of the invention relate to a wiper and seal assembly that prevents debris, such as sand particles, from entering an operating region of a pump.
Description of the Related Art
To obtain fluids from an earth formation, a wellbore is drilled into the earth to intersect an area of interest within the formation. Upon reaching the area of interest, artificial lift means is often necessary to carry production fluid (e.g. hydrocarbon fluid) from the area of interest within the wellbore to the surface. Some artificially lifted wells are equipped with sucker rod lifting systems.
Sucker rod lifting systems generally include a surface drive unit, a sucker rod string, and a downhole pump. The pump generally includes an outer barrel and an operating member, such as a plunger, axially movable within the barrel to lift fluid to the surface. The sucker rod string generally comprises several rods connected together but may be one continuous rod, and is the primary link between the drive unit at the surface and the pump plunger. In one instance, reciprocating pumping action moves a traveling valve on the pump plunger, collecting fluid on the down-stroke and lifting the fluid to the surface on the up-stroke.
Sucker rod-type lifting systems include insert pumps, where the entire assembly is run into the well with its own string of tubulars attached to the sucker rod string. These pumps are easy to get in and out of the well, but result in a smaller diameter and fluid path for the collection of hydrocarbons. Tubing pumps, on the other hand, have barrels that are actually screwed into and become part of the production string. The result is a greater capacity but difficulty in removing and repairing the barrel due to its location in the production string.
One problem associated with sucker rod lifting systems is wear within the annular region between the plunger and the barrel due to wellbore debris, such as sand. Since the annular region is typically about 0.002 inches to about 0.005 inches (per side), sand particles of various size enter the region and act as an abrasive, which quickly forms “grooves” in both the barrel and the plunger sliding surfaces. Such wear significantly diminishes the life of the barrel and the plunger, and can lead to costly repair and frequent maintenance. With tubing pumps, wear is a particular problem due to the difficulty of recovering and replacing the barrel portion of the pump.
Therefore, there is a need for an improved assembly to prevent debris from entering an operating region of a pump.